Automatic fire sprinkler systems are currently required by law be incorporated in all new commercial and high rise residential buildings, and in many localities older commercial and residential structures are being required, both for reasons of safety and for entitlement to adequate insurance coverage at reasonable premiums, to be retrofitted with such systems as well. Conventional fire sprinkler systems generally include, within each protected building space such as a room, a loft, a lobby, and the like, a horizontal water distribution pipe which extends across the top of the building space, either above or below the ceiling, and is fed from the water main of the building, and one or more sprinkler heads each of which is connected to the distribution pipe by a respective Tee or branch fitting. Each sprinkler head is provided with a water exit passageway the inlet end of which communicates with the branch fitting and therethrough with the distribution pipe. The outlet end of the water exit passageway is normally sealed by a plug which is retained in place by means of a pair of fusible metal bars anchored at one end to the sprinkler head and bearing at their other ends against the plug, so as to prevent the latter under ordinary circumstances from being ejected from the exit passageway by the pressure of the water in the distribution pipe. Should the temperature in the protected building space rise sufficiently to weaken or even melt the fusible bars, which will occur whenever a fire or a hot smoke condition exists in the protected building space, the water pressure in the distribution pipe causes the plug to be ejected from the exit passageway of the sprinkler head so as to permit the water to flow from the distribution pipe through the sprinkler head into the protected building space to douse the fire or the source of the smoke.
While fire sprinkler systems do have the capacity for minimizing incidences of injury or loss of life as well as damage to and destruction of buildings and their contents by fire, they also have one substantial drawback. That is, once the sprinkler system is set off and the water begins flowing through the sprinkler heads, there is usually no convenient way to interrupt the flow of the water other than by shutting off the main water inlet valve for the building. However, when a fire or hot smoke condition is in progress, even if it has just about been brought under control, the location of the main water inlet valve may be temporarily inaccessible, or the fire fighters and the building personnel may be too preoccupied to attend to the closing of the valve. The result then inevitably is that the continuing flow of water causes the protected building space or spaces where the fire or hot smoke condition existed to become flooded, and some of that water frequently flows into other building spaces on lower floors which per se may have been unaffected by the fire or hot smoke condition. In some cases, therefore, the property damage caused by such excess water is even greater than the damage caused by the fire or smoke condition. The continued flow of water, of course, also represents a needless waste of what, in many areas of the world, is a scarce and extremely valuable commodity.
The existence of the water damage problem, i.e., the possibility that the water damage may exceed the fire damage, has been recognized in the past, and some purported solutions to that problem have heretofore been proposed. See, for example, U.S. Pat. Nos. 260,998, 3,911,940 and 3,991,829. The proposed solutions have, however, generally involved the use of valves controlled by mechanisms which are complicated, costly to produce, maintain and replace, and uncertain of proper operation. Because of their high cost, of course, such valves and their operating mechanisms are not discarded and replaced after each operation but rather (unless they have been totally destroyed by a fire) are reused, which means that irrespective of whether the valves and their operating mechanisms are designed to reset automatically or to be reset manually, they must be individually checked and tested when the main water inlet valve is reopened.